This invention relates to a laser powered surgical instrument that employs a target for transducing laser energy into shockwaves.
The particular application of this invention is to a surgical instrument used in eye surgery and particularly for cataract removal. However, the invention may be embodied in devices which are adapted to other surgical procedures.
The use of laser energy to perform eye surgery is well known. In particular, the use of laser energy to impinge on a metal target so as to cause optical breakdown to generate shockwaves is known in applicant's U.S. Pat. No. 5,324,282. The patent discusses some of the background of the art.
More particularly, the patent discloses a design of the distal end of a surgical needle that is used for breaking up cataracts. The arrangement is one where laser pulses impinge on a target at the distal end of the needle to generate shockwaves that travel to a port of the needle at which the tissue to be fractured is positioned.
As discussed in the '282 Patent, there are a number of desirable goals for a laser operated surgical device including efficiency of operation to minimize weight, cost and size as well as to minimize heat generated and to assure maximum effect. One of the important goals is to have a minimum size diameter for the surgical instrument or the needle involved so that only a small incision need be made in the patient's eye thereby minimizing trauma and enhancing recovery. As stated in the '282 Patent, safety, comfort and minimum trauma consistent with performing the operation is the goal of the surgical instruments.
One of the instruments disclosed in the '282 Patent is disclosed herein as prior art in FIG. 5. As shown in FIG. 5, a surgical needle 50 having an O.D. of about 2.0 mm has a sidewall 52 containing an evacuating passageway 54 and an optical fiber 56 to provide pulses of laser energy. The pulses of laser energy, in one embodiment, are provided by a neodymium-YAG laser that provides light energy at a wavelength of 1,064 nano-meters. It is delivered in pulses having a width of approximately 8 nano-seconds. These pulses impinge on a target wall 58 to cause breakdown of the target and generation of plasma at the target which causes shockwaves to be transmitted to the port 60.
What has been found is that the laser pulses develop a pit in the target 58. The pit then tends to capture some of the shockwaves generated and make the application of the energy to the tissue less efficient.
In addition, particles of the vaporized target get in the path of the laser pulses thereby reducing the level of laser energy that impinges on the target and thus making the operation of the instrument less efficient.
Accordingly, a major purpose of this invention is to provide an improved surgical instrument design using the laser transducer function in which the instrument operates more effectively and efficiently and specifically to provide shockwaves that are greater in intensity at the tissue to be fractured.